The present invention relates to a rack and pinion steering gear. More particularly, the present invention relates to a rack and pinion steering gear with a pinion gear having helical teeth.
A known rack and pinion steering gear includes a housing. A rack bar extends longitudinally through the housing and has opposite ends that are connectable with the steerable wheels of the vehicle. A portion of the rack bar extending through the housing includes teeth. As the rack bar is moved linearly relative to the housing, the steerable wheels of the vehicle are turned.
The known rack and pinion steering gear also includes a pinion gear. The pinion gear includes a plurality of helical teeth. The pinion gear is located within the housing so that the helical teeth of the pinion gear are in meshing engagement with the teeth of the rack bar. The pinion gear is rotatable relative to the housing.
An input shaft extends partially into the housing. A first end of the input shaft is connectable with the steering wheel of the vehicle. A second end of the input shaft is connected with the pinion gear, generally through a torsion bar.
A roller bearing is interposed between the housing and the input shaft. The roller bearing enables rotation of the input shaft relative to the housing. Rotation of the input shaft effects rotation of the pinion gear by either directly rotating the pinion gear or by actuating a power assist motor which moves the rack bar and thus causes rotation of the pinion gear.
Rotation of the pinion gear results in a force that is directed along an axis of the input shaft. A pinion nut resists movement of the pinion gear that may result from the axial force. However, if the pinion nut loosens, the axial force may move the pinion gear axially relative to the rack bar and detrimentally affect the meshing engagement of the rack bar and pinion gear.
To prevent disengagement of the pinion gear with the rack bar in the event of a loose pinion nut, the known rack and pinion steering gear includes a retaining ring and a capture washer. The retaining ring is seated in a groove in the input shaft and is thus axially fixed to the input shaft. The capture washer is located adjacent the roller bearing and is interposed between the roller bearing and the retaining ring. When an axial force is applied to the input shaft, the input shaft moves axially until the retaining ring contacts the capture washer. The capture washer blocks further axial movement and thus, blocks further axial displacement of the pinion gear.
The present invention is a rack and pinion steering apparatus for turning steerable wheels of a vehicle in response to rotation of a steering wheel. The apparatus comprises a housing. A rack bar extends through the housing and is movable relative to the housing for turning the steerable wheels of the vehicle. The rack bar has a plurality of teeth. A pinion gear is located within the housing and is rotatable relative to the housing. The pinion gear includes a plurality of helical teeth that meshingly engage teeth of the rack bar. Engagement of the helical teeth of the pinion gear with the teeth of the rack bar during rotation of the pinion gear in a first direction results in an axial force acting on the pinion gear. A shaft is connectable with the steering wheel of the vehicle and is rotatable relative to the housing. At least a portion of the shaft extends into the housing and connects with the pinion gear. Rotation of the shaft effects rotation of the pinion gear. An assembly is interposed between the shaft and the housing. The assembly includes a first snap ring that is attached to the portion of the shaft that extends into the housing. A second snap ring is attached to the housing. Interposed between the first and second snap rings are only a fluid tight seal for blocking fluid leakage from the housing and a bushing for enabling rotation of the shaft relative to the housing. The bushing includes a radially extending surface for engaging the first snap ring to block axial displacement of the pinion gear due to the axial force acting on the pinion gear.